Data mirroring in a service

ABSTRACT

Data mirroring in a service such as a virtual private LAN service is disclosed. Data packets, segments, frames, or other forms of encapsulation may be mirrored off of a core network (e.g., IP, TCP) to one or more mirroring destinations without using a parallel network. Encapsulation techniques are provided that enable packets to be mirrored and transmitted across services such as VPLS, MPLS, and others to a mirror destination. Once received at the mirror destination, mirrored packets may be used for troubleshooting in a more efficient and less resource and time-consuming manner.

CROSS REFERENCE TO OTHER APPLICATIONS

This application is a continuation of U.S. patent application Ser. No.10/833,820, entitled DATA MIRRORING IN A SERVICE, filed Apr. 27, 2004,now U.S. Pat. No. 7,486,674 which is incorporated herein by referencefor all purposes, which claims priority to U.S. Provisional PatentApplication No. 60/466,268 entitled PACKET MIRRORING IN A VIRTUALPRIVATE LAN SERVICE ENVIRONMENT filed Apr. 28, 2003, which isincorporated herein by reference for all purposes.

FIELD OF THE INVENTION

The present invention relates generally to computer networks. Morespecifically, data mirroring in a service is disclosed.

BACKGROUND OF THE INVENTION

In computer networks, troubleshooting and administration are useful toensure quality of service (QoS), reliability, and availability.Troubleshooting and monitoring functions may be implemented by usingdata mirroring capabilities. However, data mirroring may be expensiveand limited.

Data mirroring is often implemented using a parallel network. Typically,data packets as they appear at a monitored node on a primary network aresent via the parallel network to a remote mirror node or destination.This parallel network approach requires additional hardware andsoftware, as well as significant time and labor for setup andconfiguration of a mirror network. A parallel network typically is usedto avoid having the mirror packets cause congestion or other performanceproblems on the primary network.

Therefore, it would be advantageous to be able to mirror data from anode on a primary network to a monitoring node using the primary networkitself as the transport mechanism, instead of requiring a parallelnetwork, without interfering with the delivery and processing ofnon-mirror data being sent via the primary network.

BRIEF DESCRIPTION OF THE DRAWINGS

Various embodiments of the invention are disclosed in the followingdetailed description and the accompanying drawings.

FIG. 1 illustrates an exemplary system having unidirectional transporttunnels interconnecting endpoints across a network;

FIG. 2 illustrates an exemplary forwarding engine;

FIG. 3 illustrates an exemplary system for packet mirroring;

FIG. 4 illustrates an exemplary system for packet mirroring including amirror destination;

FIG. 5 illustrates an exemplary process for packet mirroring;

FIG. 6 illustrates an exemplary flow diagram for packet mirroring;

FIG. 7 illustrates an exemplary process for ingress packet handling; and

FIG. 8 illustrates an exemplary process for egress packet handling.

DETAILED DESCRIPTION

The invention can be implemented in numerous ways, including as aprocess; an apparatus; a system; a composition of matter; a computerprogram product embodied on a computer readable storage medium; and/or aprocessor, such as a processor configured to execute instructions storedon and/or provided by a memory coupled to the processor. In thisspecification, these implementations, or any other form that theinvention may take, may be referred to as techniques. In general, theorder of the steps of disclosed processes may be altered within thescope of the invention. Unless stated otherwise, a component such as aprocessor or a memory described as being configured to perform a taskmay be implemented as a general component that is temporarily configuredto perform the task at a given time or a specific component that ismanufactured to perform the task. As used herein, the term ‘processor’refers to one or more devices, circuits, and/or processing coresconfigured to process data, such as computer program instructions.

A detailed description of one or more embodiments of the invention isprovided below along with accompanying figures that illustrate theprinciples of the invention. The invention is described in connectionwith such embodiments, but the invention is not limited to anyembodiment. The scope of the invention is limited only by the claims andthe invention encompasses numerous alternatives, modifications andequivalents. Numerous specific details are set forth in the followingdescription in order to provide a thorough understanding of theinvention. These details are provided for the purpose of example and theinvention may be practiced according to the claims without some or allof these specific details. For the purpose of clarity, technicalmaterial that is known in the technical fields related to the inventionhas not been described in detail so that the invention is notunnecessarily obscured.

Data mirroring over a network using services such as VPLS, MPLS, andothers is disclosed. Data packets, segments, frames, or other data(hereinafter “packets”) may be copied or mirrored from monitored node ona primary network to one or more mirror destinations without using aparallel network. For purposes of the following descriptions, “datamirroring” and “packet mirroring” are used interchangeably.

FIG. 1 illustrates an exemplary system 100 having unidirectionaltransport tunnels interconnecting endpoints across a network. In thisexample, data routed across this network, e.g., data transported as partof a transparent LAN service (TLS) or similar service, may be mirroredto a mirror destination, as described in greater detail below. Edgeservice routers (ESRs) 102 and 104 are connected across network 106. Inthis example, network 106 is illustrated as having an IP/MPLS corenetwork. In other embodiments, other types of core networks may be used.Customer edge routers (CEs) 108-110 send packets received from ESRs 102and 104, respectively, to the final customer destinations to which theyare addressed, such as MAC addresses within their respective customernetworks. CEs 108 and 110 also received from associated customer nodespackets to be transported using virtual leased line (VLL) service 123and deliver packets to ESRs 102 and 104, respectively, for transport.Unidirectional transport tunnels 112 and 114 provide the transportmechanism for service packet transmission. At each ESR, a servicedistribution point (SDP) is provided. In some embodiments, an SDP is asoftware object to which one or more services and one or more datatransport tunnels may be bound. By binding the services to the SDPs,instead of binding the services directly to the transport tunnels, theservices can be configured independently of the transport tunnels, andvice versa, thereby simplifying the provisioning and/or reconfigurationof each. In the example shown in FIG. 1, ESR 102 comprises SDP 124,which is shown as being bound to transport tunnel 112 to ESR 104 and ashaving VLL Service 123 bound to it via a service access point (SAP) 116,and ESR 104 comprises SDP 126, which is shown as being bound totransport tunnel 114 to ESR 102 and as having VLL Service 123 bound toit via a service access point 118. In some embodiments, a service accesspoint comprises a software object used to send and receive via aninterface to an external system, such as customer equipment connectedvia a port, data associated with a service. In some embodiments, aservice access point may be used to provide two or more “virtual” portsassociated with a single physical port.

In one embodiment, transport tunnel 112 comprises a label-switched path(LSP) associated with SDP 124 and transport tunnel 114 comprises an LSPassociated with SDP 126. Here, a service such as VLL may be implementedusing bidirectional service access points 116-118. In other embodiments,other types of service, e.g., VPLS, may be provided. Service packets areexchanged between service access points 116-118 and transported overunidirectional transport tunnels 112 and 114. In this example, virtualcircuit (VC) labels 120 and 122 are applied to the service packetsoriginating from service access points 116 and 118, respectively. SDPs124-126 forward the service packets with the appended VC labels 120-122across unidirectional transport tunnels 112 and 114 to ESRs 102-104.Upon receipt of the service packets with the prepended VC labels,de-multiplexers 128 and 130 identify the service packets as destined forservice access points 116 or 118, based on VC labels 120-122, and routethem accordingly.

In the example shown, a customer packet associated with VLL Service 123that is sent by a source associated with CE 108 to a destinationassociated with CE 110, for example, would be sent by CE 108 to ESR 102.ESR 102 would receive the packet and associate the packet with VLLservice 123 (e.g., based on the port on which it was received,encapsulation used, a label or other identifying information included inthe packet, etc.). The service access point (SAP) 116 forwards thepacket to SDP 124 (either directly in the embodiment shown or via an SDPmapping module, e.g., in an embodiment in which multiple services mayuse the same SDP) for transport to egress ESR 104. The SDP 124encapsulates the packet for transport to ESR 104 via unidirectionaltransport tunnel 112, including by appending a VC label 120 thatidentifies the packet as being associated with VLL service 123. In anembodiment in which SDP 124 comprises two or more transport tunnels toESR 104, SDP 124 selects a tunnel to be used to transport the packet toESR 104. For example, in an embodiment in which the SDP 124 comprisestwo or more LSPs, the SDP 124 may be configured to bind a service to aparticular LSP, e.g., a VLL service such as VLL Service 123, so that alltraffic for the service is sent via the same LSP. For other types ofservice (e.g., VPLS or VPRN), the SDP may map packets to an LSP fortransport by associating the packet with a “conversation” (i.e., arelated set of packets being exchanged between two endpoints) and selectan LSP associated with that conversation (e.g., to prevent packets frombeing delivered out of order, as might happen if different packetsassociated with a conversation were sent via different paths.) In someembodiments in which VPLS, VPRN, or similar service is being provided,the destination MAC address may be used to identify the LSP to be usedto transport the packet. When the packet arrives at ESR 104,de-multiplexer 130 identifies the packet as being as associated withService 123, e.g., based on the presence of VC label 120, and deliversthe original (payload) packet to SAP 118 for processing. SAP 118 thendelivers the packet to CE 110, for onward routing to its destination(e.g., host).

Service distribution points and service access points are described morefully in co-pending U.S. application Ser. No. 10/833,489, entitled USINGNETWORK TRANSPORT TUNNELS TO PROVIDE SERVICE-BASED DATA TRANSPORT, filedApr. 27, 2004, which is incorporated herein by reference for allpurposes.

Mirroring data as it appears on the wire at a network node and sendingthe mirror data (e.g., mirror packets) to a remote destination via amirroring service defined on a primary network is disclosed. As usedherein, the terms “mirror packet” and “mirrored packet” refer to apacket to be sent to a mirror destination. A “mirror” or “mirrored”packet may be the original packet (e.g., if a copy is processed forsending to the destination to which the original packet is addressed) ora copy thereof, depending on the implementation and the point at whichthe mirroring occurs (e.g., ingress or egress). Packets may be mirroredeither at ingress (i.e., in the form in which they are received at thenode) or egress (i.e., in the form in which they leave the node). Mirrorpackets are sent to a remote mirror destination via the primary network,e.g., a transport tunnel through a core network, by using a mirrorservice defined for that purpose.

FIG. 2 illustrates a forwarding engine used in some embodiments. In thisexample, a forwarding engine 202 may be implemented as one or moremodules used for both mirroring and forwarding packets from a router toa primary destination (i.e., a destination to which the packet isaddressed) and a mirror destination (i.e., the place to which you wantthe mirror packets to be sent). Forwarding engine 202 has a mirroringmodule 204 and a forwarding module 206. The mirroring module 204 in someembodiments is configured to identify packets to be mirrored (e.g.,based on criteria provided to the forwarding engine, e.g., in the formof a mirroring source object comprising such criteria) and cause theforwarding module 206 to forward such mirror packets to a mirrordestination (e.g., SDP if remote, SAP if local). The forwarding module206 uses address information to process and forward packets to theirappropriate destination.

Forwarding engine 202 provides mirroring and forwarding capabilities forpackets as they are “on the wire”, either at ingress to or egress fromthe node being monitored. For example, if mirroring is done at ingress,in some embodiments the original ingress packet is preserved and sent tothe mirror destination via a mirror service, as described more fullybelow, and a copy of the original packet is processed at the node. Forexample, in the case of a node that is a network router or switch, suchas the edge service routers described above, a packet can be mirroredeither at ingress, before the switch or router has processed it, or ategress, i.e., in the form in which it is sent out via an egress port ofthe switch or router once the switch or router has processed it. Theability to mirror at either ingress or egress is advantageous wheresignificant processing is performed at the node.

Mirrored packets may be sent to a local or remote mirror destination. Inthe case of mirroring to a local mirror destination, in some embodimentsmirror packets are sent out an egress port via a service access point(such as service access points 116 and 118 of FIG. 1) configured toserve as a local mirror destination. In the case of a remote mirrordestination, a service distribution point associated with the remotedestination may be identified as the mirror destination to which aremote forwarding engine at a monitored node sends mirror packets. Amirror service, referred to herein as a “mirror source”, is configuredto generate the mirror copies and send them to the mirror destination.The mirror packets are encapsulated and sent via a transport tunnelassociated with the service distribution point. At the far enddestination of the service distribution point, a de-multiplexer such asde-multiplexers 128 and 130 of FIG. 1 recognizes the mirror packets asbeing associated with a mirror service, based for example on a VC orother label, and forwards the mirror packets to a service access pointassociated with the mirror service. The service access point thenprovides the mirror packets via an egress port to an external systemassociated with the service (e.g., a network or system administratorconsole).

At the mirror destination, mirrored packets may be used to troubleshootnetwork conditions and problems, as the mirrored packets represent acomplete copy of packets at the monitored network node. In the case of aswitch, e.g., a copy may be obtained of packets as they enter (ingress)or exit (egress) the switch, enabling one to identify potential problemsin the way the switch is processing and/or handling packets, forexample.

FIG. 3 illustrates a typical network in which packet mirroring may beused to monitor packets as they appear at a node. Edge routers 302-308route data packets through network 300. In the example shown, it isassumed that the node to which mirror packets are to be sent (the mirrordestination) is associated with router 308. An SAP at router 308 isconfigured to operate as a mirror destination service, i.e., to receivemirror packets from either a local or remote node and provide them asoutput via an associated egress port of router 308. SDPs provided atrouters 302, 304, and 306 may be configured to send mirror packets torouter 308 using a mirror source object or process to identify thepackets to be mirrored and provide the mirror packets to a mirrordestination associated with the mirror source object or process, e.g.,via a transport tunnel associated with an SDP associated with the mirrordestination. In some embodiments, the SDP associated with the node atwhich the mirror destination is located is identified to the localmirror source object or process as the destination to which mirrorpackets are to be sent. The SDP delivers the mirror packets to the farend, where they become associated with the mirror destination SAP asdescribed above (e.g., based on a label or other identifier associatedwith the mirror service).

FIG. 4 illustrates an exemplary system for packet mirroring via a mirrorservice. In this example, SDPs 402-406 and SAP 408 comprise aunidirectional mirror service. Transport tunnels associated with SDPs402-406 may be used to route mirrored packets through SAP 408 to a host410, e.g., a network administrator's console.

Unidirectional transport tunnel services such as VPLS, MPLS, or othersmay be used for routing mirrored packets to a mirror destination such ashost 410. Host 410 may be in direct or indirect data communication withSAP 408. Here, packets may be routed across unidirectional servicetunnels from SDPs 402-406 to SAP 408. Additional encapsulation such asadded headers are attached to original packets (ingress) or copies(egress) to route them to SAP 408. The point at which packets aremirrored determines the type of packet handling.

Using a mirror service configured to send mirror packets via a primarynetwork could increase congestion on the primary network, e.g., byinterfering with the ability of a network to fulfill quality of serviceguarantees for transport services (e.g., VLAN) provided via the primarynetwork. In some embodiments, the effect of mirror service traffic isminimized by “slicing” oversized mirror packets, which reducesprocessing and time requirements, alleviating performance impacts.Mirror packets are truncated prior to being sent to a mirrordestination. Truncation minimizes replication and tunneling overheadassociated with transmitting packets to a mirror destination. In someembodiments, rate limiting is used to minimize the impact of mirrorservice packets on the performance of other services being providedusing the network by limiting the rate at which mirror packets are sentvia the mirror service. Rate limiting may be implemented with user orsystem specified limits, and may be dynamic, i.e., the permitted ratefor the mirror service may change as conditions change, e.g., the extentto which QoS guarantees are being met.

FIG. 5 illustrates an exemplary process for packet mirroring. Here, anoverall process is shown. First, a packet is identified or selected formirroring (502). The packet is copied (504). Mirror processing is thenperformed on the packet (or copy, depending on the implementation)(506). A packet may be selected for mirroring by logic included withforwarding engine 202 (FIG. 2), e.g., mirroring module 204, or a logicmodule that may be implemented as another part of system 100 (FIG. 1).In some embodiments, a mirror source object or process is configured toidentify packets to be mirrored, based on criteria provided, e.g., by anetwork administrator. In some embodiments, a “debug” or other CLI isprovided to enable an administrator to provide criteria for packetmirroring. Packet selection for mirroring may be random, according to acriterion or a set of criteria. Criteria may be user orsystem-specified. Examples of criteria for packet selection may includeport, service delimiters (e.g., VLAN tag,), MPLS or VC label, MAC or IPaddresses specified on an access control list (ACL). Other examples mayinclude criteria that specify traffic flows within a particular service.Such examples may include MAC addresses, IEEE 802.1p value and ranges,source and destination MAC addresses and ranges, Ethernet values andranges, etc. Still other examples may include source and destination IPaddresses and ranges, IP protocol values, source and destination portvalues and ranges, DiffServ Code Point (DSCP) values, IP fragments, IPoptions values and ranges, single or multiple IP options fields, and TCPACK and SYN commands (e.g., set, reset, etc.). Other criteria beyondthose described above may be used for packet selection. Criteria mayalso be used to limit packet selection.

Mirror processing as in step 506 of FIG. 5 includes determining andperforming the packet handling required to send the mirror packets tothe mirror destination. In some embodiments, a mirror source object orprocess used to send mirror packets to an associated mirror destinationtranslates the mirror packets into a form (e.g., frame type,encapsulation, etc.) that the mirror source knows the mirror destination(e.g., SDP, SAP) expects to see.

FIG. 6 illustrates an exemplary flow diagram for packet mirroring. Inthis example, a process is shown for determining the type of packethandling. Here, a decision is made as to whether a packet is to bemirrored at an ingress or an egress point relative to a switch fabric(602). If an ingress point is selected for mirroring, then ingresspacket handling is performed (604). If an egress point is selected formirroring, then egress packet handling is performed (606). Ingresspacket handling is described in greater detail in connection with FIG.7. Egress packet handling is also described in greater detail inconnection with FIG. 8.

FIG. 7 illustrates an exemplary process for ingress packet handling. Ifmirroring is to be performed at an ingress point, then an originalpacket as seen on the wire may be sent to a mirror destination, as inthis example (702). In addition to forwarding the original packet to amirror destination, changes may also be made to the packet copy made instep 504 of FIG. 5 (704). The packet copy may be processed normally,eventually arriving at the destination host port or service. In otherwords, the copy replaces the original packet and is processedaccordingly and forwarded to the original host or destination. Incontrast, the original packet may be designated as a mirrored packet, inthe case of ingress packet handling. In this example, the mirroredpacket is encapsulated and routed to a mirror destination. Routing andforwarding of the original packet to the mirror destination may includeencapsulating the packet with additional headers, labels or otherinformation. The added encapsulation may be used to route packets to amirror destination across services such as VPLS, MPLS, etc.

FIG. 8 illustrates an exemplary process for egress packet handling.Unlike ingress packet handling, normal handling is performed on theoriginal packet (egress packet), in this example (802). Here, the copyof the packet made in FIG. 5 is encapsulated for routing to a mirrordestination (804). Once encapsulated with any additional headers orlabels, the original/egress packet is forwarded to a mirror destination(806). In this example, the original packet is mirrored upon egress fromthe switch fabric of the network. At this point, the copy is made (perFIG. 5), encapsulated, and forwarded to the mirror destination. Also atthis point, the original/egress packet is processed normally andforwarded to its original destination.

Although the foregoing embodiments have been described in some detailfor purposes of clarity of understanding, the invention is not limitedto the details provided. There are many alternative ways of implementingthe invention. The disclosed embodiments are illustrative and notrestrictive.

What is claimed is:
 1. A method for packet mirroring, comprising:selecting a packet to mirror from a plurality of packets received at anode based on a mirroring criterion, the selected packet beingassociated with a service provided through a network; selecting one of aplurality of mirror points of the node based on the mirroring criterion,each of the mirror points being within a transport path for the service;preparing a mirrored packet of the selected packet at the selectedmirror point; sending the mirrored packet to a mirror destination fromthe selected mirror point using a mirror service provided through thenetwork at least via a transport tunnel; and fulfilling a quality ofservice guarantee for the service provided through the network andassociated with the selected packet to mirror at least in part bytruncating the selected packet prior to sending it via the mirrorservice, wherein the selected packet is an Internet Protocol packet,truncating the selected packet includes alleviating packet mirroringinduced increased network congestion interfering with a fulfilment ofthe quality of service guarantee by truncating content included in theInternet Protocol packet as being oversized to fulfill the quality ofservice guarantee for the service provided through the network andassociated with the selected packet to mirror, and truncating theselected packet includes truncating the Internet Protocol packet thathas been received at the node; wherein fulfilling the quality of serviceguarantee includes limiting a rate at which mirrored packets are sentvia the mirror service and limiting the rate includes dynamicallyadjusting a rate limit based on the fulfilment of the quality of serviceguarantee interfered by packet mirroring; and wherein selecting theselected packet further includes identifying the selected packet basedon one or more of the following: a user-specified criterion, asystem-specified criterion, a set of criteria, port information, adelimiter, a protocol, a label, a service or other tag, a list, anaddress, an option value, and a protocol command.
 2. A method as recitedin claim 1 further including encapsulating the mirrored packet fortransmission to the mirror destination.
 3. A method as recited in claim2 wherein encapsulating the mirrored packet includes adding informationfor routing the mirrored packet via the mirror service.
 4. A method asrecited in claim 2 wherein encapsulating the mirrored packet includesadding a header to the mirrored packet.
 5. A method as recited in claim1 wherein preparing the mirrored packet further includes copying theoriginal packet.
 6. A method as recited in claim 1 wherein preparing themirrored packet further includes performing mirror processing on thepacket.
 7. A method as recited in claim 1 wherein sending the mirroredpacket to the mirror destination includes sending the mirrored packet toa far end router associated with the mirror service.
 8. A method asrecited in claim 1 wherein sending the mirrored packet to the mirrordestination includes sending the mirrored packet to a servicedistribution point associated with the mirror service.
 9. A method asrecited in claim 1 wherein the mirror destination translates themirrored packet.
 10. A method as recited in claim 1 wherein the serviceincludes a service path.
 11. A method as recited in claim 1 wherein theservice includes a service tunnel.
 12. A method as recited in claim 1,wherein the plurality of mirror points comprise a first mirror point atan ingress point where the selected packet enters the node.
 13. A methodas recited in claim 1, wherein the plurality of mirror points comprise afirst mirror point at an egress point where the selected packet exitsthe node.
 14. A system for packet mirroring, comprising: a processorconfigured to select a packet to mirror from a plurality of packetsreceived at a node based on a mirroring criterion, the selected packetbeing associated with a service provided through a network; select oneof a plurality of mirror points of the node based on the mirroringcriterion, each of the mirror points being within a transport path forthe service; prepare a mirrored packet of the selected packet at theselected mirror point; send the mirrored packet to a mirror destinationfrom the selected mirror point using a mirror service provided throughthe network at least via a transport tunnel; and fulfil a quality ofservice guarantee for the service provided through the network andassociated with the selected packet to mirror at least in part bytruncate the selected packet prior to sending it via the mirror service,wherein the selected packet is an Internet Protocol packet, truncatingthe selected packet includes alleviating packet mirroring inducedincreased network congestion interfering with a fulfilment of thequality of service guarantee by truncating content included in theInternet Protocol packet as being oversized to fulfill the quality ofservice guarantee for the service provided through the network andassociated with the selected packet to mirror, and truncating theselected packet includes truncating the Internet Protocol packet thathas been received at the node, and wherein fulfilling the quality ofservice guarantee includes limiting a rate at which mirrored packets aresent via the mirror service and limiting the rate includes dynamicallyadjusting a rate limit based on the fulfilment of the quality of serviceguarantee interfered by packet mirroring; and wherein selecting theselected packet further includes identifying the selected packet basedon one or more of the following: a user-specified criterion, asystem-specified criterion, a set of criteria, port information, adelimiter, a protocol, a label, a service or other tag, a list, anaddress, an option value, and a protocol command; and a memory coupledto the processor and configured to provide the processor withinstructions.
 15. A system as recited in claim 14 wherein the processoris further configured to encapsulate the mirrored packet fortransmission to the mirror destination.
 16. A system as recited in claim15 wherein encapsulating the mirrored packet includes adding to themirrored packet one or more of the following: a header; and informationfor routing the mirrored packet via the mirror service.
 17. A system asrecited in claim 14 wherein the mirroring criterion comprises one ormore of the following: a user-specified criterion; a system-specifiedcriterion; a set of criteria; port information; a delimiter; a protocol;a label; a service or other tag; a list; an address; an option value;and a protocol command.
 18. A system as recited in claim 14, wherein theservice includes a service path.
 19. A system as recited in claim 14,wherein the service includes a service tunnel.
 20. A computer programproduct for packet mirroring, the computer program being embodied in anon-transitory computer readable storage medium and comprising computerinstructions for: selecting a packet to mirror from a plurality ofpackets received at a node based on a mirroring criterion, the selectedpacket being associated with a service provided through a network;selecting one of a plurality of mirror points of the node based on themirroring criterion, each of the mirror points being within a transportpath for the service; preparing a mirrored packet of the selected packetat the selected mirror point; sending the mirrored packet to a mirrordestination from the selected mirror point using a mirror serviceprovided through the network at least via a transport tunnel; andfulfilling a quality of service guarantee for the service providedthrough the network and associated with the selected packet to mirror atleast in part by truncating the selected packet prior to sending it viathe mirror service, wherein the selected packet is an Internet Protocolpacket, truncating the selected packet includes alleviating packetmirroring induced increased network congestion interfering with afulfilment of the quality of service guarantee by truncating contentincluded in the Internet Protocol packet as being oversized to fulfillthe quality of service guarantee for the service provided through thenetwork and associated with the selected packet to mirror, andtruncating the selected packet includes truncating the Internet Protocolpacket that has been received at the node; wherein fulfilling thequality of service guarantee includes limiting a rate at which mirroredpackets are sent via the mirror service and limiting the rate includesdynamically adjusting a rate limit based on the fulfilment of thequality of service guarantee interfered by packet mirroring; and whereinselecting the selected packet further includes identifying the selectedpacket based on one or more of the following: a user-specifiedcriterion, a system-specified criterion, a set of criteria, portinformation, a delimiter, a protocol, a label, a service or other tag, alist, an address, an option value, and a protocol command.
 21. Acomputer program product as recited in claim 20, further comprisingcomputer instructions for encapsulating the mirrored packet fortransmission to the mirror destination.